Preheat oven to 180°C.
In a small bowl, mix together strawberries and 2 tablespoons sugar. Let sit 15 minutes until strawberries give off juices.
In a small bowl, mix together flour, cinnamon, baking soda, nutmeg and salt.
In a large bowl, whisk together the mashed banana, eggs, oil, 225g sugar, strawberries, and lemon zest.
Mix the dry ingredients into the wet ingredients until combined. Do not over mix. Fold in blueberries and walnuts.
Scoop batter evenly into muffin cups. Bake until a toothpick inserted in center of muffin comes out with a few crumbs but not wet, about 30 minutes. Cool on a rack to room temperature.